Using Preamps In Shack
Does anyone have their preamps in the shack as opposed to mast mount? Any major disadvantage to having the preamps in the shack? I just acquired two AR2 SPxxxVDG preamps and understand they are not weatherproof and would need an enclosure to mount near antennas, which for the time being is not possible. Any thoughts would be appreciated.
Paul Delaney - K6HR [email protected] http://k6hr.dyndns.org:8080
Yes I have done this. The feed line loss will essentially add to the noise figure of the pre amp, which is not desirable, but in my case with a 70 foot run of 9913F7 the arr gasfet preamplifier was still worth using on 70 cm.
Sent from my iPad
On 2011-03-13, at 9:36 PM, "Paul Delaney - K6HR" [email protected] wrote:
Does anyone have their preamps in the shack as opposed to mast mount? Any major disadvantage to having the preamps in the shack? I just acquired two AR2 SPxxxVDG preamps and understand they are not weatherproof and would need an enclosure to mount near antennas, which for the time being is not possible. Any thoughts would be appreciated.
Paul Delaney - K6HR [email protected] http://k6hr.dyndns.org:8080
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hello
I am trying to research the SPOT messenger and GPS reporting system
I see that the band in use is 1610 - 1620 MHz
What satellites are they though ?
- Andrew -
Andrew,
The System gets it's position from the GPS satellites and reports it to it's network via the Globestar Constellation. SPOT is a subsidiary of Globestar:
http://en.wikipedia.org/wiki/SPOT_Satellite_Messenger
73 de Rick K7TEJ
---- Andrew Rich [email protected] wrote:
Hello
I am trying to research the SPOT messenger and GPS reporting system
I see that the band in use is 1610 - 1620 MHz
What satellites are they though ?
- Andrew -
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 03/16/2011 06:43 PM, Andrew Rich wrote:
Hello
I am trying to research the SPOT messenger and GPS reporting system
I see that the band in use is 1610 - 1620 MHz
What satellites are they though ?
GlobalSat.
Some interesting reading: http://natrium42.com/projects/spot/
Paul,
The main advantage of a preamp is increasing your sensitivity by lowering the noise figure of your receiving system. You lose some of that by locating the preamp in the shack. Any coax loss between the preamp and antenna adds directly to the overall NF: 80-foot of LMR-400 is 1.2 dB loss and added to a 0.5 dB NF preamp nets you a system NF = 1.2+0.5 = 1.7 dB.
But it will still increase the sensitivity of most radios that have NF in the 6 to 12 dB range.
Recently I lost one of my eme preamps on my tower and used a preamp at the shack. My normal system NF = 0.76 dB. In the shack I had 0.25 + 1.7 dB cable loss = 1.95 dB NF. That lowered my sensitivity by about 5 dB but I still received eme signals.
I would suggest you make a comparison for yourself. Try the preamp in the shack and try it near the antenna and see how much that affects your receiving ability. It is not hard to enclose a preamp inside a plastic box for outside use (a small sandwich box works).
73, Ed - KL7UW
At 08:36 PM 3/13/2011, Paul Delaney - K6HR wrote:
Does anyone have their preamps in the shack as opposed to mast mount? Any major disadvantage to having the preamps in the shack? I just acquired two AR2 SPxxxVDG preamps and understand they are not weatherproof and would need an enclosure to mount near antennas, which for the time being is not possible. Any thoughts would be appreciated.
Paul Delaney - K6HR [email protected] http://k6hr.dyndns.org:8080
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [email protected] ======================================
----- Original Message ----- From: "Edward R. Cole" [email protected] To: "Paul Delaney - K6HR" [email protected]; [email protected] Sent: Monday, March 14, 2011 7:54 AM Subject: [amsat-bb] Re: Using Preamps In Shack
Recently I lost one of my eme preamps on my tower and used a preamp at the shack. My normal system NF = 0.76 dB. In the shack I had 0.25 + 1.7 dB cable loss = 1.95 dB NF. That lowered my sensitivity by about 5 dB but I still received eme signals.
73, Ed - KL7UW
Hi Ed, KL7UW
When you write that your sensitivity lowered by about 5 dB you are absolutely correct and infact I played with numbars to verify your statement.
Your normal system NF = 0.76 dB Your normal system noise factor F = 10E (0.76/10) = 1.19 Your normal sys. noise temp. T = ( F-1) x 290 = 0.19 x 290 = 55 kelvin
In the shack system NF = 1.95 dB In the shack system noise factor F = 10E (1.95/10) = 1.56 In the shack sys noise temp. T = ( F-1) x 290 = 0.56 x 290 = 164 kelvin
Your actual reduction in S/N ratio = 10 log (55 / 164 ) = - 4.74 dB 10
You can check your actual S/N reduction of 4.74 dB receiving Sun Noise or your own Moon echoes.
By the way a reduction of about 5 dB receiving EME signals is a big S/N deterioration and so put again the preamplifier at the antenna is mandatory.
When I was on 432 MHz EME early 1977 to 1980 my array was 16 x 21 element yagi and using an antenna mounted home brewed preamplifier with a GaAsFET V-244 the Sun Noise was about 15 dB at that epoch time and it was possible for me to receive my own CW echoes from the Moon
Using a more noisy home brewed preamplifier with a bipolar transistor FJ-203F from Fujitsu antenna mounted the Sun Noise was about 10 dB but it was absolutely impossible to receive my own echoes from the moon even using my 1 kW K2RIW power amplifier.
Nice to remember but unfortunately a big storm destroyed my array at the end of 1980 !
In a separate email I have sent a picture of it.
Best 73" de
i8CVS Domenico
participants (7)
-
Andrew Rich -
Edward R. Cole -
i8cvs -
Kai Günter Brandt -
Mark Spencer -
Paul Delaney - K6HR -
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